1. Field of the Invention
This invention relates to printer control devices, and more particularly to a control device for a printer which can print out inputted data on an original (hereinafter referred to as "original data", when applicable) as hard copy.
2. Discussion of the Related Art
A conventional printer control device and a conventional printer will be described with reference to FIG. 4.
A printer control device 10 comprises a panel 11 with a ten key keyboard and other switches, an image scanner 12 for reading an original through photo-electric conversion, a sequence control section 13, and a buffer memory 14 for storing an image signal read by the image scanner 12 or an image signal of print data supplied through a network, for instance, by a work station.
The sequence control section 13 controls the operation of a printer 20 according to control data set by the panel 11 or control data supplied through the network. In this connection, the status data of the printer 20 is supplied through a line 13b to the sequence control section 13, and a variety of commands are supplied through a line 13b to the printer 20.
One or more pages of original data to be printed is stored in the buffer memory 14. When the printer 20 starts its printing operation, the sequence control section 13 provides an instruction signal, so that the original data is read out of the buffer memory 14 with predetermined timing, and applied to the printer 20.
The printer 20 comprises a laser oscillator 21, a photoreceptor 22, a developing unit 23, a transferring corotron 24, and a fixing unit 25. A printing sheet is supplied from a sheet supplying tray 26a or 26b. A toner image is transferred onto the printing sheet by the transferring corotron 24, and is then fixed by the fixing unit 25. Finally, the printing sheet is delivered into a sheet discharging tray 27.
In the printer 20 described above, the image is printed on only one side of the printing sheet. However, it should be noted that a duplex printer has been proposed in the art in which images are printed on both sides of a printing sheet. In the duplex printer, the one page of original data is printed on one side of a printing sheet in the above-described manner, and then the printing sheet is turned over and delivered to the transferring corotron 24 with predetermined timing. The toner image of the next page of original data is transferred onto the other side of the printing sheet and then fixed by the fixing unit 25. Thereafter, the printing sheet is delivered into a sheet discharging tray 27.
With the above-described printer, a variety of print data can be printed out. For instance, print data on both sides of a leaf (page) of paper in a book or the like are read with the image scanner 12, so as to be stored in the buffer memory 14 temporarily. Under this condition, the printer 20 is placed in a duplex copy mode, so that the stored print data is printed on both sides of a printing sheet. The resultant printing sheets are bound into a book similar to the original one.
Alternatively, print data of a number of pages are read through the image scanner 12 or through the network, so as to be stored in the buffer memory 14 temporarily, and are then printed out on one or both sides of a printing sheet.
The conventional printer suffers from several problems. In the case of an original like a book which has pages printed on both sides it is common for the back side of the page to be blank. In the case where such an original is copied in the duplex copy mode, it is necessary to read the blank page with the image scanner 12 similarly as in the case of ordinary pages with print. This is a wasteful operation.
On the other hand, in a printing operation, sometimes it is required to use a colored printing sheet or a formatted printing sheet for the cover or for specified pages of an original to be copied so that they be impressive. However, it is impossible for the conventional printer to meet this requirement, because in the conventional printer one sheet supplying tray is used to supply the same printing sheets for all operations.